Controlled release mechanism for balloon catheters

ABSTRACT

This invention relates to the field of balloon catheters and more particularly to catheter balloons having controlled failure mechanisms for the prevention of catastrophic failure of the balloon during overpressure conditions.

FIELD OF THE INVENTION

The present invention relates to the field of balloon catheters and moreparticularly to catheter balloons having controlled failure mechanismsfor the prevention of catastrophic failure of the balloon duringoverpressure conditions.

BACKGROUND OF THE INVENTION

Balloon catheters are used for a variety of medical procedures,including endovascular treatments. These endovascular treatments arecarried out in the lumen of a vascular duct or vessel and have theadvantage of being less aggressive and invasive than open surgery. Theirconventional use entails the insertion of the balloon catheter into abody conduit at an entrance site and pushing the length of the catheterprogressively into the body conduit until the balloon located at thedistal end of the balloon catheter reaches the desired site. The balloonis then inflated at that site in order to implement the desired therapy.The body conduit is most often a blood vessel and more particularly anartery, although balloons are used within a variety of other bodyconduits such as, for example, bile ducts. The inflation of the balloonmay be used for various therapeutic reasons. Common uses for ballooncatheters include: dilation procedures, occlusion of blood flow,delivery of a pharmaceutical composition to the specific site ofinflation, disruption of plaque or thrombus, or to deliver a device to adesired site within the body conduit. Devices most commonly deliveredwith a catheter balloon include vascular stents and intraluminalvascular grafts both of which may be circumferentially distended byinflation of the balloon until the device is implanted in firm contactwith the wall of the blood vessel or conduit.

In use, catheter balloons are known to occasionally rupture due toinflation to higher than designed for pressures. Conventional catheterballoons vent radially in the event of over-pressurization. Suddenrupture and corresponding sudden radial release of inflation pressurefluids or gases has resulted in injury to patients. During a rupture,even if the balloon remains intact, the configuration of the damagedballoon may make withdrawal of the balloon from the body conduit quitedifficult. These occasional ruptures can also result in portions of theballoon or emboli being dispersed into the blood vessel or conduit ofthe patient. Due to displacement of the fragments distally as a resultof fluid flow through the blood vessel or conduit, retrieval isdifficult and may require interventional surgery. It is furtherdifficult to ascertain with certainty that all pieces have beenretrieved. A sudden rupture and release of inflation media due toover-pressurization may also result in damage to the vessel wallrequiring additional surgery.

U.S. Pat. No. 5,221,258 to Shturman teaches a catheter balloon having alongitudinal segment of weakness intended to allow the intentionalrupture of the balloon between its ends in order to release a devicecontained within the balloon. Shturman also describes that the balloonmay be provided with a portion of larger diameter than the remainder ofthe balloon in order that the higher hoop stress in the larger diameterportion results in rupture.

U.S. Pat. No. 6,375,637 to Campbell shows a controlled failure balloonmechanism with provision of at least one aperture or slit at leastpartially through the thickness of the balloon material in at least oneend region of the balloon where it is secured to the exterior of thecatheter shaft.

None of the prior art balloon catheters provide catheter balloon sealshaving reliable and controlled failure mechanisms for the prevention ofcatastrophic failure of the balloon material during overpressureconditions. The present invention provides a balloon catheter with asafe failure design preventing fragmentation of the balloon material inthe event of a rupture and further, allowing for safe and easy retrievalof the balloon material from a patient.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a controlled pressurerelease balloon catheter device which has a predictable andnon-catastrophic controlled fail safe mechanism to prevent rupture ofthe balloon material. The present invention provides a unique ballooncatheter device which allows for controlled axial pressure release inthe event of an over-pressurized condition. The controlled pressurerelease balloon catheter is comprised of a catheter shaft having alongitudinal axis extending between a proximal end and a distal end; aninflatable balloon mounted near the catheter shaft distal end and havingtwo ends wherein at least one end of the balloon comprises an angled-cuttail; and a securing band located around at least one end of the ballooncomprising the angled-cut tail wherein the securing band holds theballoon in contact with the catheter shaft.

Another object of the present invention is to provide a controlledpressure release catheter device with a varying outer dimension on thecatheter shaft and/or balloon which allows for high pressure levels toexist within the balloon during a normal inflation pressure condition inthe balloon. The varying outer dimensions on the catheter shaft orballoon also allow for a controlled axial pressure release in the eventof excessive pressure within the balloon. The catheter shaft has alongitudinal axis extending between a proximal end and a distal end andhas a first outer dimension and a second outer dimension. The inflatableballoon is mounted near the distal end of the catheter shaft with atleast one securing band located around at least one end of the balloon.The securing band may be used to hold the balloon in contact with thecatheter shaft.

Another object of the present invention is to provide a controlledpressure release catheter with a retainer provided at the end of thecatheter shaft spaced apart from the securing band to prevent loss ofthe securing band in the event of a balloon failure. The devicecomprises a catheter shaft and inflatable balloon mounted on thecatheter shaft via at least one securing band. A retainer is spacedapart from the securing band. In the event of over-pressurization, theretainer has an outer dimension which is greater than or equal to thatof the inner dimension of the securing band to impede axial movement andprevent the securing band from breaking free of the catheter device evenat excessive pressures.

Another object of the present invention is to provide a controlledpressure release balloon catheter which withstands high inflationpressures and prevents catastrophic balloon rupture due toover-pressurization. The device has an angled-cut tail on the balloonattached via a securing band to a catheter shaft with varying outerdimensions. A retainer is further provided at the distal end of thecatheter shaft spaced apart from and distal to the securing band toprevent loss of the securing band in the event of a balloon failure.

Another object of present invention is to provide a controlled axialpressure release catheter wherein the balloon is predictably and safelyprevented from material ruptures and fragmentation duringover-pressurization by allowing controlled axial pressure release. Thesubstantially axial release of inflation media which occurs uponover-inflation of the balloon in a catheter results in a release ofinflation media in a non-perpendicular manner as related to the vesselwall. The pressure release mechanism is not directly opposed to thevessel wall thereby avoiding direct contact with the vessel wall. Thebenefit of substantial axial release of the inflation media is that thepressure exerted by the inflation media upon exit from the balloon issubstantially reduced prior to contact with the vessel wall. Thisreduced pressure may prevent the occurrence of vessel dissection orrupture. In one embodiment of the present invention the inflation mediumis released in a longitudinal direction substantially parallel to thelongitudinal axis of the catheter shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view of the distal end of a controlled pressurerelease balloon catheter prior to inflation.

FIG. 1B is an enlarged schematic end view of a controlled pressurerelease balloon catheter prior to inflation.

FIG. 2 is a sectioned view of the controlled pressure release ballooncatheter near the distal portion of the balloon.

FIGS. 3A through 3D illustrate a sequence for controlled axial pressurerelease after over-pressurization.

FIG. 3A shows a controlled pressure release balloon catheter in aninflated state.

FIG. 3B shows a controlled pressure release balloon catheter at pressureexceeding a predetermined safe inflation pressure, thus initiating axialmovement of the securing band.

FIG. 3C shows a controlled pressure release balloon catheter at apressure exceeding a predetermined safe inflation pressure, wherein thesecuring band movement is axially impeded.

FIG. 3D shows a controlled pressure release balloon catheter in anover-pressurized state venting pressure through an axial opening.

FIG. 4A shows a seal on the proximal end of a balloon catheter.

FIG. 4B is a cross-section of a seal on the proximal end of a ballooncatheter.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A is a schematic view of a non-inflated controlled pressurerelease balloon catheter device of the present invention having acontrolled failure mechanism in the form of an angled-cut tail presenton the balloon. The controlled pressure release catheter devicecomprises at least a catheter shaft, an inflatable balloon (hereinafterreferred to as balloon) with an angled-cut tail, and at least onesecuring band. The catheter shaft has a longitudinal axis 12 extendingbetween a proximal end 29 and a distal end 27 of the catheter shaft. Theballoon has two ends wherein at least one end of the balloon comprisesan angled-cut tail. For the purposes of the present invention, the endsof the balloon are those end portions of the balloon that are affixed toa shaft via a securing band 18 and any other portion of the balloon thatis on the opposite side of the securing band from the center of balloon10. The distal end of the balloon 16 is shown mounted or located at thedistal end of the catheter shaft 27. The distal end of the balloon 16constitutes the portion of the balloon 10 that is in closest proximityto the distal-most end of the catheter shaft 27 along with the tail ofthe balloon protruding from under the securing band 18. FIG. 1B shows anenlarged view of the distal end of the balloon catheter device. In thisembodiment the angled-cut tail is shown as having a short measuringportion 30 and a long measuring portion 32 located adjacent to thesecuring band 18. The retainer 26 may have a band cover 28 which may bejoined to the retainer if desired. The securing band 18 has an innerband edge 21 and an outer band edge 22 and is located around at leastone end of the balloon 10 comprising the angled-cut tail 14. The innerband edge 21 of the securing band 18 is that edge which is in closestproximity to the center of the balloon. Likewise, the outer band edge 22of the securing band is that edge which is opposite the center of theballoon 10. In FIGS. 1A and 1B, the securing band 18 holds the balloon10 in contact with the catheter shaft 20 so that over-pressurization ofthe balloon 10 allows relative movement between the securing band 18 andthe balloon 10 releasing at least a portion of the balloon from thesecuring band 10 to provide a controlled pressure release mechanism. Thesecuring band 18 is used to secure the distal end 16 of the balloon 10to the exterior surface of the catheter shaft 20, wherein the proximalcatheter shaft end 29 and the distal catheter shaft end 27 may bepresent on one shaft or may comprise ends of two or more differentshafts joined together. A similar binding or securing band 18 may beused to. constrain the proximal end 17 of balloon 10 from inflatingunder normal inflation pressure. The proximal end 17 may or may not bein contact with catheter shaft 20. As shown in FIGS. 4A and 4B, incurrent embodiment, the proximal end 17 is present on a second cathetershaft 35.

The securing band 18 may comprise any suitable elastomeric ornon-elastomeric retaining means. The securing band 18 may furtherfunction as a radiopaque marker band. Examples of suitable materials forthe securing band 18 include but are not limited to: composite metals,platinum, iridium, stainless steel, titanium, gold, biocompatiblemetals, polyethylene, polyurethanes, or biocompatible elastomers,thermoplastics, nylon, PEBA, PTFE, or any combination of materials.While the angled-cut tail 14 is shown as a beveled trailing portion oftail present on the end of a catheter mounted balloon 10, it is apparentthat an angled-cut tail 14 may be an end of any shape with a shortmeasuring portion 30 and a long measuring portion 32. As shown at FIG.2, in relation to the distal end of the balloon 16, a short measuringportion 30 has the shortest length of balloon material when measuredfrom the inner band edge 21 of the securing band 18 to the distal mostpoint of the balloon tip. Likewise, the long measuring portion 32 hasthe longest length of balloon material when measured from the inner bandedge 21 of the securing band to the distal most point of the balloontip. Suitable designs for the balloon tail include: ends with concavedesigns, notched designs, scallops, stepped designs, triangularcutaways, any other designs with a short measuring portion and a longmeasuring portion on the balloon tail. The angle associated with theangled-cut tail is measured such that a cross-section of the cathetermounted balloon could reveal two parallel balloon portions of differinglengths, namely the most proximal position on the short measuringportion 30 and the most distal position on the parallel longestmeasuring portion 32. The same concept may be applied to a securing bandcomprising a short measuring portion and a long measuring portioncoupled with either a blunt-end balloon or a balloon comprising a shortmeasuring portion and a long measuring balloon portion. The parallelmeasuring portions 30 and 32, are both intersected by a hypotheticalthird line 34, such as shown in FIG. 2. An interior angle is createdbetween the third line 34 and the parallel balloon portions when viewedin cross section. The angled-cut tail 14 is shown located at the end ofthe balloon 10. FIG. 1B shows an optional band cover 28 adjacent to theretainer 26. The retainer 26 may be rounded or tapered on the distal endto facilitate entry or insertion of the balloon catheter into a bodyconduit. The band cover may be made from a variety of materials wellknown in the art including PTFE, PET (polyethylene terephthalate), PE(polyethylene), an amide-based thermoplastic elastomer, a polyetherblock amide (PEBA), such as PEBAX™ (Arkema Chemicals), polyurethanes,polyamides, nylons and biocompatible composite materials suited for useas a band cover. The angled-cut tail 14, while shown by FIG. 1B only atthe distal end 16 of the balloon 10, may be alternatively located at theproximal end or at both ends of the balloon.

The catheter shaft 20 is shown with corresponding longitudinal axis 12and a lumen or channel extending throughout the length of the cathetershaft. The catheter shaft 20 may be made from a variety of materialswell known in the art including PTFE, PET (polyethylene terephthalate),PE (polyethylene), an amide-based thermoplastic elastomer, polyetherblock amide (PEBA), such as PEBAX™ (Arkema Chemicals), polyurethanes,polyamides, nylons, biocompatible composite materials, metals or othersuitable composites. The catheter shaft is generally a tubularconstruction and contains at least one passageway or lumen extendingbetween the distal and proximal ends of the catheter device that allowsfor passage of an inflating medium such as a saline fluid.

The catheter shaft will most generally contain at least one additionalpassageway that allows for passage of a guidewire device or otherelement.

The balloon 10 may be virtually any type of known catheter balloonincluding but not limited to: balloons made from materials such aslatex, silicone, polyurethane, biocompatible elastomers, thermoplastics,PTFE, PET (polyethylene terephthalate), or PE (polyethylene). Theballoon may also be a composite balloon such as the balloon made astaught by U.S. Pat. Nos. 5,752,934 and 5,868,704 to Campbell et al. Forthe purposes of this patent the balloon may be uni-body designed or maycomprise multiple components, such as reinforced or coated composites.

The securing bands on the distal and proximal ends may be of variousforms and materials. For instance, various elastomeric materials orvarious non-elastomeric materials may be used in the securing bands. Thesecuring band 18 may exist in forms including but not limited to:wrapped narrow strips of film or wire about the ends of the balloon,single or multiple-pieced metal bands, single or multiple-piecedcomposite bands, interlocking pieces forming a band, or any othersuitable securing band design. The proximal and distal securing bandsmay be alike or different, depending upon desired application. Thedimensions and geometric design of the securing band may also varydepending upon the desired application to incorporate features in thebands such as a tapered end on the band, a concentric band, a flared endon the band, or other desired designs. The securing band 18 may or maynot be secured by an adhesive to hold the exterior surface of theballoon in contact with the securing band.

FIG. 2 is a sectioned view of the controlled pressure release ballooncatheter near the distal portion of the balloon. In this embodiment thecontrolled pressure release catheter device comprises a catheter shaft20, an inflatable balloon 10, and a securing band 18. The inflatableballoon 10 may comprise unfolding balloons as well as expansion balloonsor any other suitable balloon or device forms. The catheter shaft 20 hasa longitudinal axis 12 extending between its proximal end 29 (not shown)of the catheter shaft 20 and the distal end 27 with a second lumen 13extending therebetween. The catheter shaft 20 further comprises a firstouter dimension of the catheter shaft 24 and a second outer dimension ofthe catheter shaft 25. The un-inflated balloon is mounted on the firstouter dimension of the catheter shaft 24 using securing bands. While theballoon in this embodiment is depicted as having an angled-cut tail, ablunt cut tail or any other tail configuration may optionally be used.The balloon 10 is located near the catheter shaft distal end 27 and hastwo ends. The securing band 18 shown in this drawing is located aroundat least one end of the balloon 10 to hold the balloon 10 in contactwith the first outer dimension of the catheter shaft 24. The secondouter dimension of the catheter shaft 25 is located distal to thesecuring band 18 and is a different diameter than the first outerdimension of the catheter shaft 24. The second outer dimension of thecatheter shaft and balloon provides resistance to axial movement of thesecuring band upon pressurization of the balloon when the diameter isequal or greater than the first outer dimension, thereby providing forthe use of a high-pressure balloon. Over-pressurization of the ballooncauses relative movement between the securing band and the balloon sothat the balloon is released from the securing band to provide acontrolled pressure release mechanism. Over-pressurization occurs when apredetermined safe inflation pressure is exceeded thereby risking afailure or rupture of the balloon 10. The predetermined safe inflationpressure is not required to be one specific inflation pressure but maybe a range of normal operating pressures. Exceeding a predetermined safeinflation pressure range occurs with pressures extending anywherebetween the normal maximum operating pressure and the burst pressure.The burst pressure is obtained when inflating medium 23 is vented due toover-pressurization. FIG. 2 shows an optional band cover 28 on thedistal end of the catheter shaft 27. A distal end of the catheter shaftis considered to be the portion of the catheter from the midsection tothe furthest most distal end. This embodiment shows varying outerdimensions as related to the catheter shaft, which prevent relativemovement between the securing band and the balloon.

In another aspect of this invention, the catheter shaft 20 may comprisea single outer diameter dimension and the balloon may comprise varyingouter dimensions. In this regard, the balloon would comprise a firstballoon outer diameter dimension and a second balloon outer diameterdimension located distal to the securing band and exhibiting a differentouter diameter measurement than the first balloon outer diameter. Thus,the balloon may comprise varying outer dimensions, which preventrelative movement between the securing band and the balloon end, with orwithout any variation in the catheter shaft outer dimensions.

FIG. 3A is a longitudinal cross section of an inflated controlledrelease balloon catheter device. In this embodiment the balloon isdepicted as having an angled-cut tail 14, however, a blunt cut tail orany other tail configuration may optionally be used. The balloon isinflated via an inflation port intended to be representative of variousknown inflation medium 23 for conveying into balloon 10 any pressurizingmedium such as a saline liquid conveyed to port via a connecting channelor lumen 11. The controlled pressure release catheter device is showncomprising a catheter shaft having a longitudinal axis 12 extendingbetween a proximal end and a distal end and a second lumen 13 extendingtherebetween. The inflatable balloon 10 has two ends mounted at thecatheter shaft distal end, with a securing band 18 located around atleast one end of the balloon 10. The securing band 18 holds the balloon10 in contact with the catheter shaft 20. The catheter shaft may extendthrough the balloon, but it is not required. A retainer 26 is providedspaced apart from and distal to the outer band edge 22.Over-pressurization of the balloon causes relative movement between thesecuring band 18 and the balloon 10 so that a portion of the balloon 10is released from the securing band 18 to provide a controlled pressurerelease mechanism. The retainer 26 prevents uncontrolled axial releaseof the securing band 18 from the catheter shaft 20. The retainer 26 maycomprise an elastomeric, non-elastomeric or thermoplastic member or anysuitable material. In certain embodiments as shown here, the retainer 26may be joined with band cover 28. The retainer may be round, conical orany other suitable shape and may be joined or extended to include a bandcover 28 which encases the securing band 18 and/or the angled-cut tail14 end of the balloon. The retainer is distinguished as having adiameter sufficient to impede marker band movement. In certainembodiments the retainer has an equal or larger outer diametermeasurement than the inner diameter measurement of the securing band.The retainer is located adjacent to the end of balloon 10 and spacedapart from the most distal part of the securing band 18. The retainerpreferably co-axially encloses the catheter shaft 20, however theretainer may be configured as a non-coaxial element. Over-pressurizationof the balloon causes relative movement between the securing band andthe balloon so that the short measuring portion of the balloon isreleased from the securing band to provide a controlled pressure releasemechanism. The release of the short measuring portion of the balloon 30from the securing band may occur due to pressurized movement of theballoon out from under the securing band, or due to longitudinalmovement of the securing band over the balloon.

During an overpressure condition, it is anticipated that the forceexerted from the balloon on the securing band 18 will increase untilfailure commences causing relative movement between the securing band 18and the balloon tail 14. In one embodiment, the second outer dimensionof the catheter shaft will prevent movement of the securing band untilsuch time as the extreme pressure of the balloon forces the securingband to transition over the catheter shaft dimension change 19 and ontothe second outer dimension of the catheter shaft, as shown in FIG. 3B.The catheter shaft dimension change 19 is a transitional area whichlinks the first outer dimension of the catheter shaft to the secondouter dimension of the catheter shaft. The movement of the securing bandcontinues until the short measuring portion of the angled-cut balloontail 14 is exposed from its previous location beneath the securing band18. Once the short measuring portion is free from the securing band, alongitudinal pressure release occurs due to inflation medium containedwithin the balloon 10 being released through the axial opening 15.Substantially axial pressure release can thus be designed to occur sothat the inflation media is directed away from the wall of the vessel.Substantially axial pressure release of inflation media is defined asoccurring upon over-inflation of the balloon catheter resulting in arelease of inflation media in a manner which directs the media in anon-perpendicular manner as related to the vessel wall. The pressurerelease mechanism is not directly opposed to the vessel wall therebyavoiding direct contact with the vessel wall. The benefit of substantialaxial release of the inflation medium is that the pressure exerted bythe inflation media upon exit from the balloon is substantially reducedprior to contact with the vessel wall. The reduced pressure prevents theoccurrence of vessel dissection or rupture. In one embodiment of thepresent invention the inflation medium is released in a longitudinaldirection substantially parallel to the catheter shaft.

In another aspect of the present invention, the securing band 18maintains hold of the longest measuring portion of the angled-cut tailto prevent disassociation of the balloon from the catheter shaft. Thesecuring band is prevented from uncontrolled axial release from thecatheter shaft by the retainer 26. The balloon material thus, remainsintact and attached to the catheter shaft via the securing band and isable to be easily withdrawn from within the body conduit.

In one preferred embodiment, the controlled pressure release catheterdevice comprises a catheter shaft 20 having a longitudinal axis 12extending between a proximal end 17 and a distal end 16 wherein thecatheter shaft 20 comprises a first outer dimension 24 and a secondouter dimension 25; an inflatable balloon 10 comprised of ePTFE ismounted near the catheter shaft distal end 27. The inflatable balloon 10has two ends wherein at least one end of the balloon comprises anangled-cut tail 14; a securing band 18 comprising a metal composite,such as platinum and iridium is located around at least one end of theballoon comprising an angled-cut tail. The securing band holds theballoon in contact with the first outer dimension of the catheter shaft.A second outer dimension of the catheter shaft is located distal to thesecuring band and is greater than the first outer dimension, therebyproviding resistance to axial movement of the securing band uponpressurization of the balloon. A retainer is provided at the distal endof the balloon and is spaced distal to and apart from the securing band18. The retainer is joined to a band cover, to form a single unit whichco-axially encases the distal end of the balloon, the catheter shaftdimension change 19 and the securing band 18 when the balloon is in anon-inflated state. In this embodiment the band cover and the retainer26 are comprised of a polyether block amide, namely a plasticizer freethermoplastic elastomer, such as PEBAX™ (Arkema Chemicals), as shown inFIGS. 3C and 3D. As the balloon reaches a predetermined failurepressure, the balloon begins to exert the necessary force against thesecuring band 18 to cause relative movement between the securing band 18and the balloon 10 resulting in at least a portion of the balloon 10being released from the securing band 18. Once a portion of the balloonis released from the securing band 18 to form the axial opening 15 onthe balloon, a pressure release occurs axially to safely vent in thepath of the conduit or vessel, and prevent vessel rupture. The balloon10 remains intact and at least a portion of the balloon 10 continues tobe held to the catheter shaft by the securing band. The retainerprevents uncontrolled axial release of the securing band from thecatheter shaft as shown in FIG. 3C.

The size of the securing band and the proximity of securing band to thedistal end 16 of the inflated balloon 10 will be dependent upon desiredapplications. The balloon design including the balloon type, angle ofcut on the balloon tail, balloon material and the varying outerdimensions of a balloon will need to be engineered for desiredapplications. Similarly, the catheter shaft material, catheter shaftdimensions, and the first outer dimension and second outer dimension ofthe catheter shaft will be designed for their desired application.

FIGS. 4A and 4B show seals on the proximal end of a balloon 10 mountedon the distal end of the catheter shaft 20. The securing band 18, theretainer 26, and the band cover 28 in FIG. 4A are shown mounted to asecond catheter shaft 35. The second catheter shaft 35 and the firstcatheter shaft 20 enclose the inflation lumen 11. The inner dimension ofthe first catheter shaft 20 provides the second lumen 13, as shown inFIG. 4B. Alternatively, multiple lumens may exist within one cathetershaft.

In this embodiment, the proximal catheter shaft end 29 and the distalcatheter shaft end comprise ends of different shafts. An angled-cut tail14 is shown having a short measuring portion 30 and a long measuringportion 32. In FIG. 4B the balloon dimension change 39 is shown asadjacent to a second catheter shaft 35 with the transition from thefirst outer balloon dimension 37 to the second outer balloon dimension38.

A guide wire lumen 13 extends throughout a portion or all of the balloon10. The space in inflation lumen 11 is pressurized with inflation mediumso that expansion or unfolding of the balloon 10 occurs. Pressure fromthe inflation medium 23 causes relative movement between the securingband 18 and the balloon 10. In this FIG. 4B an angled-cut tail 14 isshown, however, any tail shape could be substituted as desired.

In order to ensure that failure begins at a particular end, if that isdesired, for example at a securing band 18 on the distal end rather thanat the proximal end, the securing band on the proximal end should bemade to provide greater resistance to relative movement between thesecuring band and balloon tail than the distal securing band. This maybe accomplished by various methods including the use of a wider orthicker material for the proximal securing band. This may alternativelybe accomplished through the use of a longer or non-angled balloon tailon the preferred non-failing end. Generally, any desired method may beused which provides for greater resistance to translation of thesecuring band at one end than the other, allowing the weaker end to failat a predetermined inflation pressure.

While the principles of the invention have been made clear in theillustrative embodiments set forth herein, it will be obvious to thoseskilled in the art to make various modifications to the structure,arrangement, proportion, elements, materials and components used in thepractice of the invention. For example, the FIGS. 1A-3D depict adifference between the first outer dimension of the catheter shaft andthe second outer dimension of the catheter shaft which allow for acontrolled axial pressure release in the event of excessive pressurewithin the balloon. It would be within the skill of one in the art tocreate a catheter shaft with a constant outer dimension used with aballoon having a varying outer first and second dimension to provide thesame benefits. In these variations, the balloon comprises a longitudinalaxis extending between a proximal balloon end and a distal balloon end.The balloon first outer dimension is larger than the distally locatedballoon second outer dimension. The inflatable balloon is mounted nearthe distal end of the catheter shaft with a securing band located aroundat least one end of the balloon to hold the balloon in contact with theconstant outer dimension of the catheter shaft. During an overpressurecondition, it is the force exerted from the balloon on the securing band18 which will increase until failure commences causing the securing band18 to move axially from the balloon first outer dimension toward theballoon second outer dimension. To the extent that these variousmodifications do not depart from the spirit and scope of the appendedclaims, they are intended to be encompassed therein.

1. A controlled pressure release catheter device comprising: a cathetershaft having a longitudinal axis extending between a proximal end and adistal end; an inflatable balloon mounted near the catheter shaft distalend and having two ends wherein at least one end of the ballooncomprises an angled-cut tail; and a securing band located around atleast one end of the balloon comprising the angled-cut tail.
 2. Acontrolled pressure release catheter device comprising: a catheter shafthaving a longitudinal axis extending between a proximal end and a distalend wherein the catheter shaft comprises a first outer dimension and asecond outer dimension; an inflatable balloon mounted near the cathetershaft distal end and having two ends; and a securing band located aroundat least one end of the balloon, wherein the second outer dimension ofthe catheter shaft is located on the opposite side of the securing bandfrom the center of the balloon and is different than said first outerdimension.
 3. A controlled pressure release catheter device comprising:a catheter shaft having a longitudinal axis extending between a proximalend and a distal end; an inflatable balloon mounted on the cathetershaft and having two ends; a securing band located around at least oneend of the balloon; and a retainer provided on the catheter shaft andspaced apart from the securing band.
 4. The controlled pressure releasecatheter device of claim 3 wherein the catheter shaft comprises a firstcatheter shaft outer dimension and a second catheter shaft outerdimension.
 5. The controlled pressure release catheter device of claim 4wherein the second catheter shaft outer dimension is greater than thefirst catheter shaft outer dimension.
 6. The controlled pressure releasecatheter device of claim 4 wherein the securing band is located on thefirst catheter shaft outer dimension prior to balloon inflation
 7. Thecontrolled pressure release catheter device of claim 3 wherein theinflatable balloon comprises a first balloon outer dimension and asecond balloon outer dimension.
 8. The controlled pressure releasecatheter device of claim 7 wherein the second balloon outer dimension isgreater than the first balloon outer dimension.
 9. The controlledpressure release catheter device of claim 8 wherein the securing band islocated on the first balloon outer dimension prior to balloon inflation10. A controlled pressure release catheter device comprising: a cathetershaft having a longitudinal axis extending between a proximal end and adistal end wherein the catheter shaft comprises a first outer dimensionand a second outer dimension; an inflatable balloon mounted near thecatheter shaft distal end and having two ends wherein at least one endof the balloon comprises an angled-cut tail; a securing band locatedaround at least one end of the balloon comprising an angled-cut tail andholding the balloon in contact with the first outer dimension of thecatheter shaft wherein the second outer dimension of the catheter shaftis located on the opposite side of the securing band from the center ofthe balloon and is different than said first outer dimension; and aretainer provided on the at least one end of said balloon and spacedapart from the securing band.
 11. The controlled pressure releasecatheter device of claim 10 wherein the second catheter shaft outerdimension is greater than the first catheter shaft outer dimension. 12.The controlled pressure release catheter device of claim 10 wherein thesecuring band is on at least the proximal end of the balloon.
 13. Thecontrolled pressure release catheter device of claim 10 wherein thesecuring band is on at least the distal end of the balloon.
 14. Thecontrolled pressure release catheter device of claim 10 furthercomprising a band cover.
 15. The controlled pressure release catheterdevice of claim 13 wherein the band cover is a thermoplastic.
 16. Thecontrolled pressure release catheter device of claim 14 wherein thethermoplastic is a polyether block amide.
 17. The controlled pressurerelease catheter device of claim 10 wherein the retainer is joined tothe band cover on the distal end of the catheter.
 18. The controlledpressure release catheter device of claim 13 wherein the band cover isan elastomer.
 19. A controlled axial pressure release cathetercomprising: a catheter shaft having a longitudinal axis extendingbetween a proximal end and a distal end wherein the catheter shaftcomprises a first outer dimension and a second outer dimension; aninflatable balloon mounted near the catheter shaft distal end and havingtwo ends wherein at least one end of the balloon comprises an angled-cuttail; and a securing band located around at least one end of the ballooncomprising an angled-cut tail and holding the balloon in contact withthe first outer dimension of the catheter shaft wherein the second outerdimension of the catheter shaft is located on the opposite side of thesecuring band from the center of the balloon and is different than saidfirst outer dimension
 20. A controlled pressure release catheter ofclaim 1, 10 or 19 where the pressure release mechanism provides for asubstantially axial release of inflation media.
 21. The controlledpressure release catheter of claim 1, 10, 19 where the pressure releasemechanism reduces the pressure exerted by the inflation media upon exitfrom the balloon and prior to contact with the vessel wall.
 22. Thecontrolled pressure release catheter of claim 19 where the pressurerelease mechanism is spaced apart from the vessel wall.
 23. A method foraxial release of inflation medium in a balloon catheter at anintravascular site, comprising the steps of: providing the controlledpressure release catheter device of claim 1; introducing the controlledpressure release catheter device into the vasculature advancing thecontrolled pressure release catheter device through the vasculature toposition the balloon at the intravascular site; and expanding theballoon against the vascular wall at the intravascular site; wherein thecontrolled pressure release catheter device releases inflation mediumaxially in the event of excess pressure.
 24. A method for axial releaseof inflation medium in a controlled pressure release balloon catheter atan intravascular site, comprising the steps of: Introducing thecontrolled pressure release balloon catheter device into thevasculature, advancing the controlled pressure release balloon catheterthrough the vasculature to an intravascular site, expanding the balloonagainst the vessel wall and in the event of excess pressure, releasingthe inflation medium axially.
 25. A method for axial release ofinflation medium in a balloon catheter at an intravascular site,comprising the steps of: providing the controlled pressure releasecatheter device of claim 10; introducing the controlled pressure releasecatheter device into the vasculature advancing the controlled pressurerelease catheter device through the vasculature to position the balloonat the intravascular site; and expanding the balloon against thevascular wall at the intravascular site; wherein the controlled pressurerelease catheter device releases inflation medium axially in the eventof excess pressure.
 26. A method for axial release of inflation mediumin a balloon catheter at an intravascular site, comprising the steps of:providing the controlled pressure release catheter device of claim 19;introducing the controlled pressure release catheter device into thevasculature advancing the controlled pressure release catheter devicethrough the vasculature to position the balloon at the intravascularsite; and expanding the balloon against the vascular wall at theintravascular site; wherein the controlled pressure release catheterdevice releases inflation medium axially in the event of excesspressure.
 27. A controlled pressure release catheter device comprising:a catheter shaft having a longitudinal axis extending between a proximalend and a distal end; an inflatable balloon comprising a first balloonouter dimension and a second balloon outer dimension mounted near thecatheter shaft distal end and having two ends; and a securing bandlocated around at least one end of the balloon, wherein the secondballoon outer dimension is located on the opposite side of the securingband from the center of the balloon and is different than said firstballoon outer dimension
 28. The controlled pressure release catheterdevice of claim 10 wherein the second catheter shaft outer dimension isgreater than the first catheter shaft outer dimension.